One thing you can do is buy a can of that compressed air that you get for computer keyboards, etc. Get some very small diameter hose that fits perfectly on the straw that you get with the can of air and hand feed the tube down the drain. Give the hose a good shot of air as your feeding it down the drain. This compressed air is very high pressure and should dislodge or blow out whatever may be clogging it up.

Good luck.

__________________
Frank
84 500SEL EURO 101K ( JUST LIKE MY 1ST WIFE. GLAD TO GET RID OF HER! )
85 300D 310K (sold)
90 350SDL 184K sold
83 300D 118K (sold)
88 300E 153k (sold)
93 400E 105K (sold)